Synopsis: The principle of nuclear magnetic resonance and its usefulness in the fields of biochemistry and biophysics are described. The proton 220 MHz resonance spectrum of flavin adenine dinucleotide was taken. From the analysis of the spectrum a probable structure of FAD in aqueous solution was proposed, where the adenine and isoalloxazine rings are stacked with their long axes perpendicular to each other. Although the model is the most stable one, whole structure in solution may be explained by the dynamical equilibrium among several folded and open forms. $^{13}C$ resonance spectrum of phosphatidylethanolamine is also given. Its statical and dynamical structure is discussed.